In a statement, a spokesperson for the Northern Ireland Fire and Rescue Service said the firefighting operation is being scaled down.
Initially, nine fire appliances and 49 firefighters were deployed to the incident at a Church of Ireland on Station Road in Greenisland.
But, NIFRS said this has been reduced to three pumps that will remain at the scene through the night.The cause of the fire has yet to be determined.
"We would advise members of the public to avoid the area where possible and nearby homeowners to keep their windows and doors closed," a NIFR spokesperson said.